During the initial script for Resident Evil 2 (now called BIOHAZARD 1.5) by Hideki Kamiya, Ada was originally an Umbrella researcher named Linda, who would help Leon during his scenario, being responsible for guiding him through the city's sewers to a factory formerly used by Umbrella and after tasked he to create a vaccine with she to save Marvin Branagh, who had been infected by the mutant William Birkin before she was killed by one of the creatures contained within the underground laboratory. She also would not have romance with Leon. In her early concept art, her outfit designs mainly consisted of the same red sweater and black pants, along with a small necklace. One concept showed a large green jacket with an Umbrella logo on the back. In the final design, she wore a white Umbrella lab coat, red shirt, khaki shorts, red shoes, and a necklace.
Already in the redefinition of the Noboru Sugimura's script, the name "Ada" was conceived by Kazunori Kadoi to provide a link to John Clemens, the Arklay Laboratory's head researcher mentioned in the original Resident Evil, and her story's scenario was changed. With regard to her design reformulation, due the former series producer Shinji Mikami is a big time film buff, the character of Ada Wong has quite a few similarities to the protagonist of Nikita (La Femme Nikita); Both are women who have been "reborn" in one way or another, signified by a scene where they look into a mirror and vow to leave their past behind. They are femme fatale archetypes, skilled female assassins and super spies who work for a mysterious organization. Are deadly in more ways than one, equally adept at weaponry, combat, and assassination as they are with using their feminine wiles to catch unsuspecting men off guard. Ada and Nikita also share one major flaw in their assassin career, a love for a man: in this case, Marco for Nikita and Leon for Ada. They often find themselves unable to go through with certain orders due to a conflict with their feelings for a man they love. Both women even have a very shady black-clad superior whose cool exterior hides a ruthless nature they answer to: Michael for Nikita, and Wesker for Ada. Lastly, Separate Ways' title screen for Resident Evil 4 even resembles the poster for Nikita's movie.